1. Field of the Invention
This invention relates generally to abrading material and more specifically, to improvements to cutting teeth for etched metallic abrading sheets which are suitable for use in handheld power tools and the like.
2. Description of the Prior Art
Abrading devices and more particularly, etched abrading devices are known in the art as well as methods of making abrading devices. Briefly, there are basically two general types of abrading devices, the metallic abeading devices and the non-metallic abrading devices. The non-metallic abrading devices are characterized by the sheet materials which are commercially known and sold as sandpapers. Metallic abrading devices are generally used for harder materials and include devices such as rasps, files and the like. Within this general category of metallic abrading devices, there is an etched abrading device which is capable of abrading in the same manner as sandpaper yet has considerable greater durability and life than sandpaper. A typical example of this type of abrading device is shown in the McDermott U.S. Pat. No. 3,045,321 which is assigned to the same assignee as the present invention. Typically, the McDermott type of abrading material is etched from metallic sheet material. A portion of the material is etched away to leave a set of regular sharp points for use in abrading the material away. The McDermott type of abrading device utilizes the principle of sharp points which penetrate the surface of the material to be abraded. While abrading rapidly, the McDermott type of abrading device is best suited for producing a roughened rather than a smooth finish.
Another embodiment of the metallic type of etched abrading device is shown in the Davidson U.S. Pat. No. 852,873 in which a knife sharpener is produced by partially undercutting the resist layer to produce a series of regular elongated undercut edges. Davidson suggests that his elongated undercut edges can be used for sharpening knives and the like.
While McDermott and Davidson prior art devices have been known for some time, they have not gained wide acceptance because of certain drawbacks such as the clogging of the abrading material and the inability of the abrading devices to flex and withstand the stress encountered with high speed rotary abrading operations. A cutting tool such as Davidson plugs up quite readily if used in high speed operation with a soft material. Furthermore, the Davidson device is inflexible and will not conform to the surface of the material to be abraded. While abrading cylinders or drums can be made from flat abrading sheets such as McDermott, they do have a drawback as they are difficult to form the cylinders for use in high speed operation. An improvement to this type of abrading device for use in drums is shown and described in the co-pending application of Herbert M. Bond, Ser. No. 237,734, filed March 24, 1972 now abandoned, titled "Abrading Devices" in which improvements to teeth spacing and fastening are described to provide an improved abrading device that has long life and is non-clogging.
The present invention, in contrast to these prior art etched abrading devices, comprises an improvement to the teeth of the etched abrading device. That is, the present invention provides a set of cutting teeth or posts which do not penetrate the material to be abraded. This is in direct contrast to prior art etched abrasives which have sharp points to penetrate the surface of the material being abraded. The present invention is found to provide a smoother finish than prior art devices with a cutting rate and abrasive life better than prior art etched abrasives.
Thus, the present invention eliminates the problems of furrowing or gouging associated with the cutting teeth of the prior art etched abrasive materials utilizing sharp points. An added feature is that the elimination of the furrowing has not been done at the expense of either the life of the abrading article or the cutting efficiency of the abrading material. Therefore, the present invention has its greatest utility where it is desired to rapidly cut a smooth surface. However, if a roughened surface is desired, the McDermott device would be preferred.
Another aspect of the invention is that certain ranges of abrasive sizes have been found which insure that one can provide an etched abrasive set of cutting teeth which will coact smoothly and effectively to rapidly abrade away material.